Patent application title: SCALE

Abstract:

A scale includes a platform, load sensors provided at four corners inside
the platform, and a display unit. Each load sensor has an elongate load
cell and a strain gauge. Each load cell is arranged such that its
longitudinal direction is approximately orthogonal to the direction
connecting heel and toe of the foot placed on the platform. The display
unit is arranged at a central portion of the platform, and feet-receiving
regions are set at opposite sides of the display unit. By such a
structure, a scale allowing reduction in size while preventing
degradation of measurement accuracy as much as possible can be realized.

Claims:

1. A scale, comprising:a platform including feet-receiving regions,load
sensors provided at four corners inside the platform; anda display unit;
whereinsaid load sensors each include an elongate load cell and a strain
gauge;said elongate load cell is arranged with its longitudinal direction
arranged approximately orthogonal to a direction connecting heel and toe
of the foot placed on said platform;said display unit is arranged at a
central portion of said platform; andsaid feet-receiving regions are
provided on opposite sides of said display unit.

2. The scale according to claim 1, whereinangle of inclination of said
feet-receiving regions is different from angle of inclination of a region
outside of said feet-receiving regions.

3. The scale according to claim 1, whereinlength of said platform in a
direction connecting heel and toe of the foot is shorter than the length
of said platform in the longitudinal direction of said elongate load
cells.

4. The scale according to claim 1, whereinsaid platform further includes a
current electrode and a voltage electrode for the left foot and a current
electrode and a voltage electrode for the right foot, on said
feet-receiving regions;said scale further comprisinga body composition
calculating unit causing a current to flow from said current electrodes
to human body, detecting a voltage at said voltage electrodes, and
calculating body composition of said human body using the detected
voltage value.

5. The scale according to claim 4, whereinlateral width of said current
electrode and said voltage electrode in the longitudinal direction of
said elongate load cells corresponds to lateral width of the foot placed
on said platform.

Description:

[0004]A scale using load sensors having load cells generally includes a
platform, load sensors provided at four corners inside the platform, and
a display unit. Here, the display unit is arranged at a central portion
on the front side of the platform, and feet-receiving regions are set on
opposite, left and right sides of the display unit.

[0005]For measuring weight using the scale as such, the user stands on the
platform with his/her left and right feet placed on the feet-receiving
regions. Feet size and shape vary widely and, therefore, the positions
where the left and right feet are received naturally vary person to
person, both in front/rear and left/right directions, and the positions
of the left and right feet of even one user received on feet-receiving
regions may vary both in front/rear and left/right directions every time
he/she measures weight. This means that load point for a load cell in
each load sensor varies at every measurement, which affects measurement
accuracy. In order to solve this problem, load cells 110 positioned at
four corners in a scale 100 are arranged such that longitudinal
directions of the cells are substantially aligned with the diagonals of
scale 100, as shown in FIG. 13. By such an arrangement, even if the left
and right feet-receiving positions should vary in front/rear and
left/right directions, decrease in measurement accuracy can be prevented.

[0006]In an example of such a scale, the load cells are arranged along the
diagonals of a weighing plate, with one end of respective cells being in
contact with four corners of the weighing plate (for example, see
Japanese Utility Model Registration No. 3128216).

[0007]Another example has been known in which load cells arranged at
corners (four corners) of a stage each include a corner arrangement
portion of the same shape as the corner, a slit provided at the center, a
strain portion consisting of a cantilever-type piece formed by the slit,
and a strain gauge arranged at the root side of the strain portion, and
the load cells are positioned with the pieces arranged along the
diagonals of the stage (for example, see Japanese Patent Laying-Open No.
2003-149038).

[0008]When one stands on the scale as described above, feet positions tend
to fluctuate in the front/rear direction rather than the left/right
direction, as it is easier ergonomically to recognize deviation in the
left/right direction than the front/rear direction.

[0009]In this regard, in the scales described in Japanese Utility Model
Registration No. 3128216 and Japanese Patent Laying-Open No. 2003-149038,
load cells are arranged along the diagonals of the platform to prevent
degradation of measurement accuracy derived from variation of
feet-receiving positions both in the front/rear and left/right
directions, and therefore, both front/rear and left/right directions are
susceptible to the influence of unfair values and, as a result, further
improvement in measurement accuracy has been difficult.

[0010]Further, because of the manner of arranging load cells, the platform
(that is, the scale) must have a shape sufficiently large both in the
front/rear and left/right directions. Specifically, with the conventional
arrangement of load cells, degradation of measurement accuracy caused by
deviation in feet-receiving positions both in the front/rear and
left/right directions cannot satisfactorily be prevented no matter
whether the platform is vertically long, that is, large in front/rear
direction or horizontally long, that is, large in left/right direction.
Therefore, the scales described in Japanese Utility Model Registration
No. 3128216 and Japanese Patent Laying-Open No. 2003-149038 both have
substantially square shape of a certain size as a whole.

[0011]There is a demand for a scale allowing further reduction in size
while preventing degradation in measurement accuracy as much as possible
and, the conventional scales described above cannot meet such a demand.

SUMMARY OF THE INVENTION

[0012]Therefore, an object of the present invention is to provide a scale
allowing further reduction in size while preventing degradation of
measurement accuracy as much as possible.

[0013]In order to attain the above-described object, the present invention
provides a scale, including a platform, load sensors provided at four
corner portions inside the platform, and a display unit; wherein the load
sensors each include an elongate load cell and a strain gauge; the
elongate load cell is arranged with its longitudinal direction
approximately orthogonal to the direction (front/rear direction)
connecting one's heel and toe of the foot placed on the platform (aligned
with the left/right direction); the display unit is arranged at the
center of the platform; and feet-receiving regions are provided on
opposite sides of the display unit.

[0014]Focusing on the tendency that feet-receiving positions deviate in
the front/rear direction rather than left/right direction when the user
stands on the platform with his/her left and right feet positioned on the
feet-receiving regions, in the scale, the load cells are arranged such
that longitudinal direction of the load cells are aligned with the
aforementioned orthogonal direction (left/right direction), so that error
in measurement caused by the positional deviation in the front/rear
direction can more effectively be compensated for. Thus, coupled with the
tendency described above, further improvement of measurement accuracy can
be attained.

[0015]Preferably, in the scale, the feet-receiving region has an angle of
inclination different from that of a region outside the feet-receiving
region (end portion). With the feet-receiving regions formed in this
manner, coupled with the tendency that positional deviation in left/right
direction is less likely than in the front/rear direction, deviation of
feet-receiving positions in the left/right direction becomes much less
likely. Specifically, when the user places his/her feet on the end
portions of feet-receiving regions, he/she feels as if his/her feet slip
or fall from the platform and, to avoid such situation, the user makes a
conscious effort to surely place the feet on the feet-receiving regions.
Thus, measurement accuracy can further be improved.

[0016]Further, in the scale described above, preferably, length in the
direction connecting one's heel and toe (front/rear direction) of the
platform is shorter than the longitudinal direction (left/right
direction) of the elongate load cell of the platform (that is, the
platform is horizontally long). In the scale of the present invention,
load cell is arranged with its longitudinal direction aligned with the
left/right direction and, therefore, even if the length of the platform
in front/rear direction is short and the feet-receiving positions should
deviate in the front/rear direction, the positional deviation in the
front/rear direction hardly deflects the load cell and hence, the load
cell is not influenced by the positional deviation in the front/rear
direction. By this structure, it becomes possible to make the scale
compact, as the length in the front/rear direction of the platform is
shorter.

[0017]The scale of the present invention has the basic structure for
measuring weight, and, in addition, the platform may include a current
electrode and a voltage electrode for the left foot and a current
electrode and a voltage electrode for the right foot provided at the
feet-receiving regions. The scale may further include a body composition
calculating unit, causing a current to flow through the human body from
the current electrode, detecting a voltage at the voltage electrode and
calculating, using the detected voltage value, human body composition (at
least one of body fat ratio, body fat amount and body fat volume). This
allows measurement of not only weight but also body composition.

[0018]Here, desirably, the lateral width of the current electrode and the
voltage electrode in the longitudinal direction of the elongate load cell
corresponds to the lateral width of one's foot placed on the platform. By
such an arrangement, when one places his/her feet on the feet-receiving
regions of the platform, the foot surely contacts the current electrode
and the voltage electrode, and measurement accuracy of body composition
can be improved.

[0019]The foregoing and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in conjunction
with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a plan view (top view) of a scale in accordance with an
embodiment of the present invention.

[0021]FIG. 2 is a bottom view of the scale shown in FIG. 1.

[0022]FIG. 3A is a front view of the scale viewed from the direction of
arrow A shown in FIG. 1.

[0023]FIG. 3B is a side view of the scale viewed from the direction of
arrow B shown in FIG. 1.

[0024]FIG. 4 is an enlarged cross-sectional view of a portion surrounded
by circle C of FIG. 3A.

[0025]FIG. 5 is an enlarged cross-sectional view of a portion surrounded
by circle D of FIG. 3B.

[0026]FIG. 6 is a perspective view showing an appearance of a load sensor
provided in the scale shown in FIG. 1.

[0027]FIG. 7 is a side view of the load sensor provided in the scale shown
in FIG. 1.

[0028]FIG. 8 is an exploded perspective view of the load sensor provided
in the scale shown in FIG. 1.

[0029]FIG. 9 is a plan view (top view) of the scale shown in FIG. 1.

[0030]FIG. 10A shows positions of left and right feet when one stands on
the "front side" of the platform.

[0031]FIG. 10B shows positions of left and right feet when one stands on
the "rear side" of the platform.

[0032]FIG. 10C is a graph representing measurement error caused by
positional deviation of feet in the front/rear direction, of a
comparative example of "diagonal arrangement" in which the longitudinal
direction of the load cell is aligned with the diagonal of the platform
and of the embodiment of "parallel arrangement" in which the longitudinal
direction of the load cell is aligned with the left/right direction.

[0033]FIG. 11A shows positions of left and right feet when one stands on
the "right side" of the platform.

[0034]FIG. 11B shows positions of left and right feet when one stands on
the "left side" of the platform.

[0035]FIG. 11C is a graph representing measurement error caused by
positional deviation of feet in the left/right direction, of a
comparative example of "diagonal arrangement" in which the longitudinal
direction of the load cell is aligned with the diagonal of the platform
and of the embodiment of "parallel arrangement" in which the longitudinal
direction of the load cell is aligned with the left/right direction.

[0036]FIG. 12 is a schematic illustration showing direction of load cell
arrangement in the scale in accordance with the embodiment shown in FIG.
1.

[0037]FIG. 13 is a schematic illustration showing direction of load cell
arrangement in the conventional example.

[0038]FIG. 14 is a functional block diagram of the scale shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039]In the following, an embodiment of the present invention will be
described.

[0040]FIG. 1 is a plan view (top view), FIG. 2 is a bottom view, FIG. 3A
is a front view from the direction of arrow A of FIG. 1 and FIG. 3B is a
side view from the direction of arrow B shown in FIG. 1, of the scale in
accordance with the embodiment.

[0041]The scale measures not only weight but also body composition (body
fat ratio, body fat amount and body fat volume), and has a platform 1 as
the main body. At the central portion of the platform 1 (central portion
in the left/right direction), a display unit (liquid crystal display) 5
displaying the weight measurement or body composition and an operation
unit 6 are provided. On opposite, left and right sides of the display
unit and operation unit 6, left foot receiving region 1L and a right foot
receiving region 1R are set. On foot-receiving region 1L, a current
electrode 2L and a voltage electrode 3L for the left foot are provided,
and on foot-receiving region 1R, a current electrode 2R and a voltage
electrode 3R are provided.

[0042]One characteristic (hereinafter referred to as the first
characteristic) of the scale is that, when we represent the direction
connecting the heel and toe of left and right feet placed on
feet-receiving regions 1L and 1R, that is, the direction connecting
electrodes 2L and 3L for the left foot and connecting electrodes 2R and
3R for the right foot as the front/rear direction (Y-axis direction) and
the direction orthogonal thereto as the left/right direction (X-axis
direction), the platform 1 is set to have the length b in the Y-axis
direction shorter than the length a in the X-axis direction, that is, the
platform has a horizontally long shape.

[0043]At four corners inside the platform 1, load sensors 10L, 11L, 10R
and 11R also serving as legs for supporting platform 1 are arranged. Each
of the load sensors 10L, 10R, 11L and 11R has an elongate load cell 30
and an elongate strain gauge 35, which will be described later. Further,
on the back side of platform 1, a battery cover 13 is provided.

[0044]Next, the load sensors 10L, 10R, 11L and 11R as another
characteristic portion of the scale will be described. FIG. 4 is an
enlarged cross section of a portion surrounded by circle C of FIG. 3A,
FIG. 5 shows an enlarged cross section of a portion surrounded by circle
D of FIG. 3B, FIG. 6 is a perspective view showing the appearance of the
load sensor, FIG. 7 is a side view and FIG. 8 is an exploded perspective
view, of the load sensor.

[0045]As is best shown in FIG. 8, load sensor 11R (same in 10L, 11L and
10R) includes a circular top plate 21, a circular bottom plate 22, and a
load cell 30 posed between top plate 21 and bottom plate 22. Top plate 21
has a recess 21a, and a screw insertion hole 21b is formed in recess 21a.
Bottom plate 22 has a protrusion 22a, and a screw insertion hole 22b is
formed in protrusion 22a.

[0046]Load cell 30 has an elongate shape and has screw holes 31 and 32 at
opposite ends. At a recessed portion 33 between screw holes 31 and 32, an
elongate strain gauge 35 is attached. The longitudinal direction of load
cell 30 is set to be the same as the longitudinal direction of strain
gauge 35. Load cell 30 is set to a state posed between top plate 21 and
bottom plate 22 when a screw 23 inserted through screw insertion hole 21b
of top plate 21 is screwed in screw hole 31 and a screw 24 inserted
through screw insertion hole 22b of bottom plate 22 is screwed in screw
hole 32. Specifically, load cell 30 is set to a "beam" state with its one
end supported by top plate 21 and the other end supported by bottom plate
22.

[0047]Load sensor 11R having such a structure is fixed to weighing plate
40 by a screw 27 at a corner inside the platform 1. Thus, bottom plate 22
protruding from the backside of platform 1 comes to be in contact with
the scale-mounting surface. Accordingly, load to the feet-receiving
surface of platform 1 is applied to four load sensors 10L, 10R, 11L and
11R through weighing plate 40 and load cells 30 as "beams" deflect.
Correspondingly, strain gauge 35 is deflected and the load is detected in
accordance with the amount of deflection.

[0048]Another characteristic (hereinafter referred to as the second
characteristic) of the scale is that load cell 30 of each of the load
sensors 10L, 11L, 10R and 11R is arranged such that its longitudinal
direction is aligned with the direction (X-axis direction) orthogonal to
the direction (Y-axis direction) connecting electrodes 2L and 3L for the
left foot and electrodes 2R and 3R for the right foot.

[0049]A still further characteristic (hereinafter referred to as the third
characteristic) is that though feet-receiving regions 1L and 1R are
substantially flat as a whole, outer sides (end portions both in the
front/rear and left/right directions) have larger angle of inclination,
as can be seen from FIGS. 3 to 5. Specifically, platform 1 has steeply
curved surface from the top to the side surface.

[0050]Because of the first characteristic that the length b in the Y-axis
direction of platform 1 is shorter than the length a in the X-axis
direction (b<a), the scale (or platform 1) can be made compact.

[0051]Further, because of the second and third characteristics, a scale
having high measurement accuracy, which is not susceptible to the
influence of deviation of feet-receiving positions, can be realized.
Specifically, there is inherently a tendency that positional deviation in
left/right direction is less likely than in the front/rear direction as
described above, and in the scale, platform 1 is adapted to have the
shape of the third characteristic, so as to make use of the tendency. The
third characteristic makes positional deviation in the left/right
direction much less likely. The reason is that when the user places
his/her feet on the end portions of feet-receiving regions 1L and 1R,
he/she feels as if his/her feet slip or fall from the platform and to
avoid such situation, the user makes a conscious effort to surely place
the feet on the feet-receiving regions 1L and 1R.

[0052]The scale can be made compact because of the first characteristic as
described above, while positional deviation in the front/rear direction
influences measurement accuracy, as the length b of the scale in the
front/rear direction is short. Such influence, however, can sufficiently
be reduced by the second characteristic described above. When the second
characteristic is adopted, load cells 30 come to be arranged along the
left/right direction and load cells are hardly deflected by positional
deviation in the front/rear direction, so that they are almost free of
any influence of positional deviation in the front/rear direction.

[0053]Therefore, the scale, though compact in size, attains high
measurement accuracy, not influenced by the deviation of feet positions
in the left/right and front/rear directions, because of synergetic effect
of the first to third characteristics described above.

[0054]Such effects of the scale will be described with reference to
experimental results. FIGS. 10A to 10C and 11A to 11C represent the
experiment in which 10 subjects measured weights three times each, in
accordance with the instruction to "stand on the `front side`, `rear
side`, `right side` and `left side`", and the average error of weight
measurements of each subject was compared.

[0055]FIG. 10A indicates positions of left foot FL and right foot FR when
one stands on the "front side" of platform 1, and FIG. 10B indicates
positions of left foot FL and right foot FR when one stands on the "rear
side" of platform 1. In FIG. 10C showing the result, "diagonal"
arrangement represents an example in which longitudinal direction of the
load cells is aligned with the diagonal of the platform (diagonals
assuming platform 1 to be a rectangle, even if it is oval) as a
comparative example, and "parallel" arrangement represents an example in
which longitudinal direction of the load cells is aligned with the
left/right direction (X-axis direction) as the embodiment. It can be seen
that, for all subjects, error is smaller in "parallel" arrangement than
"diagonal" arrangement and that the embodiment of the invention is less
susceptible to the influence of positional deviation in the front/rear
direction than the comparative example.

[0056]FIG. 11A indicates positions of left foot FL and right foot FR when
one stands on the "right side" of platform 1, and FIG. 11B indicates
positions of left foot FL and right foot FR when one stands on the "left
side" of platform 1. From FIG. 11C showing the result, it can be seen
that error in the "parallel" arrangement is smaller for only two
subjects. For the remaining 8 subjects with large errors, the errors in
the "parallel" arrangement and "diagonal" arrangement were compared.
Absolute values of errors in general were smaller than the front/rear
direction shown in FIG. 10C, and the influence of positional deviation in
the left/right direction is not much different from the "diagonal"
arrangement. The reason for this is that inherently the influence to the
measurement accuracy of positional deviation in the front/rear direction
is large than in the left/right direction. Therefore, it can be
understood that the embodiment, which can better lessen the influence of
positional deviation in the front/rear direction, attains sufficiently
higher measurement accuracy than the comparative example.

[0057]When body composition is to be measured using the scale in
accordance with the embodiment, referring to FIG. 14, to the left and
right feet in contact with electrodes 2L and 3L for the left foot and
electrodes 2R and 3R for the right foot, a current applying unit 51 of a
body composition calculating unit 50 causes a current to flow to the body
through current electrodes 2L and 2R, a voltage detecting unit 52 of body
composition calculating unit 50 detects voltages at voltage electrodes 3L
and 3R, and using the detected voltage values, body composition
calculating unit 50 calculates the body composition.

[0058]Here, it is desirable that lateral width (length in the left/right
direction) of current electrodes 2L and 2R and voltage electrodes 3L and
3R corresponds to the width of feet placed on platform 1. Then, when one
places his/her feet on feet-receiving regions 1L and 1R of platform 1,
his/her feet surely contact current electrodes 2L and 2R as well as
voltage electrodes 3L and 3R, and measurement accuracy of body
composition can be improved.

[0059]Although the present invention has been described and illustrated in
detail, it is clearly understood that the same is by way of illustration
and example only and is not to be taken by way of limitation, the scope
of the present invention being interpreted by the terms of the appended
claims.